1. Field of the Invention
The present invention relates to an apparatus and method for testing and monitoring an optical fiber network from a central station using a single set of testing and monitoring equipment.
2. Description of the Prior Art
There are many applications that utilize an optical fiber network to establish communication links between a host digital terminal (HDT) at a central office and an optical network unit (ONU) at a remote location. Rarely does a single fiber extend the full length between the HDT and the ONU without disruption. Rather, optical fiber networks contain many remote stations between the HDT and the ONU. At the various remote stations, optical signals are regenerated to compensate for transmission losses that occur in the optical fibers. Furthermore, remote stations are also used as splicing stations where different optical fiber cables are spliced together.
Many remote stations in an optical fiber network are unmanned and operate in a fully automated fashion. At such remote stations, automated operations are controlled by a fiber administration system that organizes the various optical fibers that lead into, and away from, the remote station. The fiber administration system contains a station systems controller that is the computer control for the fiber administration system.
In the fiber administration system, the various optical fibers are directed into an optical distribution frame where the individual optical fibers are terminated in an organized manner. Such fiber administration systems are exemplified by the LGX(copyright) fiber administration system which is currently manufactured by Lucent Technologies of Murray Hill, N.J., the assignee herein.
A primary piece of equipment used to test and characterizes optical pathways in an optical fiber network is an optical time domain reflectometer (OTDR). OTDR are not only capable of characterizing the transmission qualities of an optical pathway, they also are capable of determining where in an optical pathway a fatal defect has occurred. Because of their versatility, it is desirable to have an OTDR at every remote station in an optical fiber network. However, OTDRs are very expensive. For that reason, it is not practical to buy an OTDR for each remote station. Rather, it is more cost effective to periodically dispatch a technician to the various remote stations with an OTDR. Once at a remote station, the technician can attach to OTDR to the various optical fibers and perform the required testing.
Dispatching technicians to remote stations to manually connect and disconnect test equipment is an expensive and time consuming endeavor. If a technician is sent to a remote location to test for the location of a broken optical fiber, it may be several hours before the exact location of the broken optical fiber can be located.
A need therefore exists for an apparatus and method whereby a single set of testing equipment can be used to test remote stations of an optical fiber network in an automated fashion thereby eliminating the need for redundant testing equipment and technicians who haul and install the redundant test equipment at the various remote stations.
The present invention is an apparatus and method for testing at least a portion of an optical fiber network from various remote stations without having optical testing equipment at those remote stations. The apparatus and method utilize a series of routers that are located at the central office and the remote stations of an optical fiber network. The routers are interconnected through a common optical pathway that is part of the optical fiber network. Testing equipment is located at the central office of the optical fiber network. Test signals and command signals generated by the test equipment and fiber administration system at the central office are directed to the router module at the central office. The router at the central office multiplexes these signals and forwards these signals into the optical fiber network.
The router at the remote station removes the multiplexed signal from the optical fiber network. Once removed, the test signals and command signals are utilized at the remote station to test at least a portion of the optical fiber network from that remote station. The router at the remote station provides the required testing signals even though no testing equipment is physically present at the remote location.